Most rotary fluid machines are capable of reverse operation. As a result, operation in one direction will cause the device to function as a pump or compressor while reverse operation will have the device operating as an expander. Normally, the fluid machine will be installed in a system where reverse flow and operation are not wanted. Specifically, where a rotary machine is intended to be operated as a pump or compressor, upon shutoff, there will be a pressure differential between suction and discharge which will tend to cause the machine to operate as an expander. A check valve is commonly used to prevent the discharge and suction sides from equalizing through the compressor. If follows that the reverse operation, if any, will be a function of the mass of a gas available for reverse flow and its pressure.
Commonly assigned U.S. Pat. No. 4,904,165 discloses a comornec muffler, separator plate and check valve for a hermetic scroll compressor. This design, however, does not address reducing the dimensions of the compressor package. Further, the muffler portion is just a chamber defined in part by perforated sheet metal.